Electron beam apparatuses, in particular a scanning electron microscope (also referred to as SEM below) and/or a transmission electron microscope (also referred to as TEM below), are used to examine objects (also referred to as samples) in order to obtain knowledge in respect of the properties and behavior of the objects under certain conditions.
In an SEM, an electron beam (also referred to as primary electron beam below) is generated by means of a beam generator and focused on an object to be examined by way of a beam guiding system. The primary electron beam is guided in a gridshaped manner over a surface of the object to be examined by way of a deflection device. Here, the electrons of the primary electron beam interact with the object to be examined. Interaction particles and/or interaction radiation is/are produced as a result of the interaction. By way of example, the interaction particles are electrons. In particular, electrons are emitted by the object—the so-called secondary electrons—and electrons of the primary electron beam are scattered back—the so-called backscattered electrons. The secondary electrons and backscattered electrons are detected by means of at least one particle detector. The particle detector generates detection signals, which are used to generate an image of the object. Thus, an image of the object to be examined is obtained. By way of example, the interaction radiation comprises x-ray radiation and/or cathodoluminescence radiation. The interaction radiation is detected by means of at least one radiation detector, which generates detection signals. By way of example, these detection signals are used to generate spectra, by means of which properties of the object to be examined are determined.
In a TEM, a primary electron beam is likewise generated by means of a beam generator and focused on an object to be examined by means of a beam guiding system. The primary electron beam passes through the object to be examined. When the primary electron beam passes through the object to be examined, the electrons of the primary electron beam interact with the material of the object to be examined. The electrons passing through the object to be examined are imaged onto a luminescent screen or onto a detector—for example in the form of a camera—by a system consisting of an objective. By way of example, the aforementioned system additionally also comprises a projection lens. Here, imaging can also take place in the scanning mode of a TEM. Such a TEM is generally referred to as STEM. Additionally, provision can be made for detecting electrons scattered back at the object to be examined and/or secondary electrons emitted by the object to be examined by means of a further detector in order to image an object to be examined.
The integration of the function of an STEM and an SEM in a single particle beam apparatus is known. It is therefore possible to carry out examinations of objects with an SEM function and/or with an STEM function using this particle beam apparatus.
Furthermore, the prior art has disclosed the practice of analyzing and/or processing an object in a particle beam apparatus using, firstly, electrons and, secondly, ions. By way of example, an electron beam column having the function of an SEM is arranged at the particle beam apparatus. Additionally, an ion beam column is arranged at the particle beam apparatus. Ions used for processing an object are generated by means of an ion beam generator arranged in the ion beam column. By way of example, material of the object is ablated or material is applied onto the object during the processing. The ions are additionally or alternatively used for imaging. The electron beam column with the SEM function serves, in particular, for observing the processing of the object, but it also serves for further examination of the processed or non-processed object.
It is known to detect the interaction particles and/or the interaction radiation with, firstly, a segmented detector and, secondly, a pixel-based detector. This will be explained in more detail below.
The segmented detector has a number of detector segments, wherein each one of the detector segments is respectively connected to an amplifier unit, wherein each amplifier unit in turn is connected to respectively one readout electronics unit. Each individual detector segment has a number of detection units. By way of example, each one of the detection units is respectively embodied as a semiconductor element. As soon as one of the detection units of a detector segment detects interaction particles and/or interaction radiation, a detection signal is generated by this detector segment. Each one of the detector segments generates detection signals. The detection signals of each detector segment are amplified by the amplifier unit associated with the detector segment and subsequently read by the readout electronics unit associated with the detector segment. Known segmented detectors have e.g. up to ten detector segments. This relatively low number of detector segments enables a relatively quick read out of the detection signals from the detector segments.
A known use of a segmented detector lies in the generation of a three-dimensional representation of an object, which is analyzed in a particle beam apparatus. In this known use, images are produced by means of a particle beam using a plurality of detector segments of the segmented detector. The detector segments of the segmented detector are arranged symmetrically about an optical axis of the particle beam apparatus, along which optical axis the particle beam is guided to the object. By way of example, the particle beam is embodied as an electron beam. In particular, the use of a segmented detector with four detector segments is known. Each one of the detector segments generates detection signals, which are respectively used for the image generation. Respectively one image of the object is generated by each one of the detector segments such that a total of four images is generated by means of the known segmented detector. Using the four generated images, gradients along a first axis (e.g. an x-axis) and along a second axis (e.g. a y-axis) are determined for the surface of the object. A grid of profiles, which can be assembled to form a three-dimensional model of the object, is obtained by integrating the gradients along the first axis and the second axis.
As already mentioned above, it is known to detect the interaction particles and/or the interaction radiation using a pixel-based detector. A pixel-based detector is based on the use of semiconductor elements and it is embodied e.g. as a CCD unit or as a CMOS unit. Each pixel is formed by respectively one semiconductor element or respectively one scintillation element. Using such a detector, it is possible, for example, to combine mutually adjacent pixels to form a pixel block. By way of example, a pixel block has m rows and n columns of pixels, with m and n being integers. The pixel block can also be referred to as detector segment. When the semiconductor element or the scintillation element of a pixel detects interaction particles and/or interaction radiation, a detection signal is generated and output as a signal of the pixel block—i.e. as a signal of all the pixels contained in the pixel block.
In the case of the pixel-based detector, it is furthermore possible to subsequently combine groups of pixels to form detector segments after producing an image of the object, as will be explained below. Firstly, an image of the object is recorded using all pixels in the pixel-based detector. After recording the image, groups of pixels are combined to form detector segments visually by means of software or on a monitor. A further image is generated subsequent thereto. The further image is generated by detecting interaction particles and/or interaction radiation by means of the pixel-based detector. The further image is calculated subsequent thereto by means of software, taking into account the determined detector segments, and it is subsequently displayed.
In the known pixel-based detectors, it is disadvantageous that, firstly, the recording speed is low and that, secondly, large amounts of data need to be processed and stored.
In the known segmented detectors, it is disadvantageous that the size and the location of the arrangement of the detector segments at a detection surface of the segmented detector are fixedly prescribed.
In respect to the prior art, reference is made in an exemplary manner to U.S. Pat. No. 8,450,820 B2, US 2013/0037715 A1, U.S. Pat. No. 8,629,395 B2, U.S. Pat. No. 4,897,545, a publication entitled “A high-speed area detector for novel imaging techniques in a scanning transmission electron microscope” by Caswell et al. in Ultramicroscopy 109 (2009) 304-311 and a publication about an x-ray beam device entitled “Differential phase contrast with a segmented detector in a scanning X-ray microprobe” by Hornberger et al in J. Synchrotron Rad. (2008), 15, 355, 362, all of which are incorporated by reference herein.
Accordingly, it is desirable to be able to analyze an object using an analysis apparatus, e.g. a particle beam apparatus or an x-ray beam device, and provide an analysis apparatus for analyzing an object using an analysis apparatus, which, firstly, enables a relatively quick recording of an image of the object and, secondly, enables a high resolution and a good contrast of the image.